[MlMt] Keyboard shortcuts to jump to specific panes

[Kai Großjohann]

I don't know why, but I feel the strong urge to focus the "list of 
messages" pane when I want to move between messages using j/k and n/p.  
And with Tab and Shift-Tab it gets a bit old, as I never know how often 
I have to hit them.  Usually I overshoot.

WIBNI there was a key that always focused the list of messages (say g 
followed by g), another key that always focused the message (say g 
followed by m), andother that always focused the list of folders (say g 
followed by f)?

Kai